Thanks to KacosPro, we've identified the cause: Firefox's new Tracking Protection blocks these images:

screenshot showing tracking protection enabled in Firefox along with niels nielsen's profile (and blocked image)

Some member's picture displays as a white square instead of real picture. For example there https://physics.stackexchange.com/users, the user niels nelsen shows as a white square, but not on Windows. When I click on his profile, something even stranger happens, the top half of his picture is grey, the bottom half is white.

The exact same bug happens for some members only. Let me provide a few of them: https://physics.stackexchange.com/users/40292/niels-nielsen, https://physics.stackexchange.com/users/132371/%c3%81rp%c3%a1d-szendrei, https://physics.stackexchange.com/users/68181/time4tea, and https://physics.stackexchange.com/users/176409/snoob-dogg.

Happy debugging!

Edit: Apparently some people believe(d) the ISP was blocking "graph.facebook.com", or something like that. A ping test as well as connections using a browser to graph.facebook.com, fbcdn.net and this link seem to point out that the domain is in fact not blocked. Thus, to me, the mystery is still not elucidated.

Adding a picture of the whole thing. bug

  • 1
    No repro for me on Mac. These images are all from Facebook. Are you blocking Facebook? – Laurel Oct 3 '18 at 19:54
  • Not really. I tried on Firefox (with some blockers that I just disabled, but that didn't help), also with Tor Browser. Same problem in both browsers. – AccidentalBismuthTransform Oct 3 '18 at 20:01
  • Can you check the console/network tabs in dev tools? Any errors? – Suvitruf - Andrei Apanasik Oct 3 '18 at 21:02
  • You appear to have graph.facebook.com blocked so the pictures aren't able to load. Nothing we can really do about that. – animuson Oct 3 '18 at 21:51
  • @animuson well, SE can upload the pictures to the dedicated imgur host. This way everyone would only have to make sure one single domain is whitelisted to see all profile pictures. – Shadow Wizard is Vaccinating Oct 3 '18 at 22:20
  • @ShadowWizard That... doesn't make any sense at all. The point of linking directly to an external source is so that if the user updates it wherever they're pulling from, it updates here too. It's the same premise as using Gravatar. Saving everything to Imgur completely disallows users from utilizing that functionality. – animuson Oct 3 '18 at 22:27
  • I'm on Linux, and I can see neils picture correctly – DarkCygnus Oct 3 '18 at 23:53
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    @DarkCygnus it got nothing to do with browser or OS. The block is network level, e.g. blocked by companies who don't want their employees to use Facebook while working, so they just block the whole domain. – Shadow Wizard is Vaccinating Oct 4 '18 at 6:51
  • @animuson Not sure why you think I have graph.facebook.com blocked. Disabling all addons on Firefox doesn't fix the issue, and typing "ping graph.facebook.com" in a terminal shows that it is not blocked whatsoever. – AccidentalBismuthTransform Oct 4 '18 at 7:44
  • @ShadowWizard Is there a conclusive test I can do to check whether it is blocked in my networks? Because typing "ping graph.facebook.com" does not give any such clue, it just transmits packets without any packet loss. – AccidentalBismuthTransform Oct 4 '18 at 7:45
  • Ping isn't reliable way, you need to test via a browser, or software simulating browser request. SE doesn't have such tools. – Shadow Wizard is Vaccinating Oct 4 '18 at 7:46
  • It's as simple as just browsing to graph.facebook.com. What do you see when visiting the link? – Shadow Wizard is Vaccinating Oct 4 '18 at 8:21
  • @ShadowWizard I get an error: "Unsupported get request. Please read the Graph API documentation at developers.facebook.com/docs/graph-api". – AccidentalBismuthTransform Oct 4 '18 at 8:49
  • 3
    It's because of Firefox tracking protection. It happens for me always on macOS too. When the shield appears on the url bar is because it blocked some parts of the page – user384394 Oct 4 '18 at 13:34
  • 1
    @KacosPro Spot on! That was it... Could you please post it as answer? – AccidentalBismuthTransform Oct 4 '18 at 14:23

It's because of Firefox Tracking Protection, as far as I know it will happen on all OS, it happens for me on macOS too.

Image showing Firefox tracking protection on action

When this shield appears on the url bar is because it blocked some parts of the page

  • 1
    Mozilla showing us the error of our ways. – Jeremy Oct 4 '18 at 16:37
  • @Guest Mozilla should show an indication in the replacement picture that it was blocked. Now I clicked tooling support, got shown an image which wasn't blocked (!) and had to browse the internet and ask other mods what the heck was going on. – Maarten Bodewes Feb 14 '19 at 21:56

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